title: Baculum morphology predicts reproductive success of male house mice under sexual selection.
abstract: BACKGROUND
  Diversity in penile morphology is characterised by extraordinary variation in the size and shape of the baculum (penis bone) found in many mammals. Although functionally enigmatic, diversity in baculum form is hypothesised to result from sexual selection. According to this hypothesis, the baculum should influence the outcome of reproductive competition among males within promiscuous mating systems. However, a test of this key prediction is currently lacking.
  
  
  RESULTS
  Here we show that baculum size explains significant variation in the reproductive success of male house mice under competitive conditions. After controlling for body size and other reproductive traits, the width (but not length) of the house mouse baculum predicts both the mean number of offspring sired per litter and total number of offspring sired.
  
  
  CONCLUSIONS
  By providing the first evidence linking baculum morphology to male reproductive success, our results support the hypothesis that evolutionary diversity in baculum form is driven by sexual selection.
authors.affiliation: Mammalian Behaviour & Evolution Group, Department of Evolution, Ecology and Behaviour, University of Liverpool, Leahurst Campus, Chester High Road, Neston CH64 7TE, UK. p.stockley@liv.ac.uk
authors.forename: Paula
authors.initials: P
authors.lastname: Stockley
authors.forename: Steven A
authors.initials: SA
authors.lastname: Ramm
authors.forename: Amy L
authors.initials: AL
authors.lastname: Sherborne
authors.forename: Michael D F
authors.initials: MD
authors.lastname: Thom
authors.forename: Steve
authors.initials: S
authors.lastname: Paterson
authors.forename: Jane L
authors.initials: JL
authors.lastname: Hurst
mesh_terms: D000818:Animals; D005260:Female; D008297:Male; D052586:Mating Preference, Animal / Q000502:physiology*; D051379:Mice; D009929:Organ Size; D010413:Penis / Q000033:anatomy & histology*; D019655:Quantitative Trait, Heritable; D012098:Reproduction / Q000502:physiology*